Guy Woppelmann

La Rochelle Université

We investigated the long-term changes of the principal tidal component M2 over the North Atlantic coasts, from 1846 to 2018. We analysed 9 tide gauges with time series starting no later than 1920. The longest is Brest with 165 years of observations. We carefully processed the data, particularly to remove the 18.6-year nodal modulation. We found tha...

We review the status of current sea-level observing systems with a focus on the coastal zone. Tide gauges are the major source of coastal sea-level observations monitoring most of the world coastlines, although with limited extent in Africa and part of South America. The longest tide gauge records, however, are unevenly distributed and mostly conce...

Monitoring and Predicting Regional to Coastal Sea Level: Towards Comprehensive Observing and Modeling Systems

This study proposes a method for the cross calibration of tide gauges. Based on the combination of at least three collocated sea level time series, it takes advantage of the least squares variance component estimation (LS-VCE) method to assess both sea level biases and uncertainties in real conditions. The method was applied to a multi-instrument e...

A major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of...

Coastal zones are highly dynamical systems affected by a variety of natural and anthropogenic forcing factors that include sea level rise, extreme events, local oceanic and atmospheric processes, ground subsidence, etc. However, so far, they remain poorly monitored on a global scale. To better understand changes affecting world coastal zones and to...

Coastal populations are impacted by relative sea level variations, which consist both of absolute sea level variations and of vertical land motions. This paper focuses on the Southwest and Central Pacific region, a recognized vulnerable region to sea level rise and where a large range of vertical land motion dynamics is observed. We analyse vertica...

Relative sea-level rise and the influence of vertical land motion at Tropical Pacific Islands (Supplementary material)

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

In spite of the recent advances and the current perspectives of satellite radar altimetry to reach the coastline and monitor coastal sea level changes, this space-borne technology remains geocentric by essence. In contrast, the quantity that matters for coastal management and society is relative sea level. That is, the sea level relative to the lan...

Abstract Sandy shorelines are constantly evolving, threatening frequently human assets such as buildings or transport infrastructure. In these environments, sea-level rise will exacerbate coastal erosion to an amount which remains uncertain. Sandy shoreline change projections inherit the uncertainties of future mean sea-level changes, of vertical g...

Sandy shorelines are constantly evolving, threatening frequently human assets such as buildings or transport infrastructures. In these environments, sea level rise will exacerbate coastal erosion to an amount which remains uncertain. Sandy shoreline change projections inherits the uncertainties of future mean sea level changes, of vertical ground m...

Le projet PAMELi (Plateforme Autonome Multicapteurs pour l'Exploration Littorale interdisciplinaire) porte sur l'observation répétée des paramètres environnementaux tels que les paramètres physico-chimiques de la colonne d'eau, la qualité des eaux, la hauteur d'eau et la bathymétrie précise à l'aide d'un drone marin. Ce projet sera mis en place dan...

Le littoral est un système dynamique complexe régi par les interactions entre divers processus physiques, biologiques ou humains. Mieux comprendre ces interactions nécessite l'acquisition simultanée et répétée de données de divers capteurs. PAMELi sera un drone marin destiné à acquérir des données scientifiques multidisciplinaires en domaine littor...

The GNSS-Acoustics (GNSS-A) method couples acoustics with GNSS to allow the precise localization of a seafloor reference in a global frame. This method can extend on-shore GNSS networks and allows the monitoring of hazardous oceanic tectonic phenomena. The goal of this study is to test the influence of both acoustics ray tracing techniques and spat...

Assessing the vertical land motion (VLM) at tide gauges (TG) is crucial to understanding global and regional mean sea-level changes (SLC) over the last century. However, estimating VLM with accuracy better than a few tenths of a millimeter per year is not a trivial undertaking and many factors, including the reference frame uncertainty, must be con...

Significance Estimates of global mean sea level (GMSL) before the advent of satellite altimetry vary widely, mainly because of the uneven coverage and limited temporal sampling of tide gauge records, which track local sea level rather than the global mean. Here we introduce an approach that combines recent advances in solid Earth and geoid correcti...

Up-to-date monthly time series of Northern Hemisphere atmospheric circulation pattern indices (1950–2015 CE) were retrieved from the Climate Prediction Center, NOAA. The study focused on the NAO, East Atlantic (EA) and East Atlantic–West Russia (EA–WR) patterns, which are the first three dominant patterns involved in wave climate variability across...

Accurate measurements of changes in sea and land levels with location and time require making precise, repeated geodetic ties between tide gauges and satellite positioning system equipment.

Present-day coastal barriers represent around 15% of the world’s oceanic shorelines, and play an important role as early warning indicators of environmental change. Among them, wave-dominated barriers are dynamic landforms that tend to migrate landward in response to storms and sea-level change. High rates of sediment supply can locally offset the...

Vertical land motions are a key element in understanding how sea levels have changed over the past century and how future sea levels may impact coastal areas. Ideally, to be useful in long-term sea level studies, vertical land motion should be determined with standard errors that are 1 order of magnitude lower than the contemporary climate signals...

With growing concerns regarding future impacts of sea-level in major coastal cities, the most accurate information is required regarding local sea-level changes with respect to the coast. Besides global and regional sea-level changes, local coastal vertical ground motions can substantially contribute to local changes in sea-level. In some cases, su...

We review the measurement of the mean dynamic topography (MDT) of the Mediterranean using ellipsoidal heights of sea level at discrete tide gauge locations, and across the entire basin using satellite altimetry, subtracting estimates of the geoid obtained from recent models. This ‘geodetic approach’ to the determination of the MDT can be compared t...

With growing concerns regarding future impacts of sea-level in major coastal cities, the most accurate information is required regarding local sea-level changes with respect to the coast. Besides global and regional sea-level changes, local coastal vertical ground motions can substantially contribute to local changes in sea-level. In some cases, su...

Maison de la Chimie, side event de la conférence "Our Common Future under Climate Change"

Before the altimetry era, tide gauges are a unique source of information to evaluate past sea-level changes. However, they can be affected by vertical ground motions acting at different space scales. We use Synthetic Aperture Radar Interferometry techniques to assess these ground motions and their consequences for key geodetic instruments such as T...

Résumé L’arc des petites Antilles est situé à proximité d’une frontière de plaques en subduction et de ce fait, l’aléa sismique y est important. Pourtant, peu de grands événements ont été recensés, ce qui peut être lié à la nature de la zone ou à la trop courte période d’observation. Actuellement, nous n’avons pas les éléments pour écarter définiti...

This paper describes the historical sea level data that we have rescued from a tide gauge, especially devised originally for geodesy. This gauge was installed in Marseille in 1884 with the primary objective of defining the origin of the height system in France. Hourly values for 1885–1988 have been digitized from the original tidal charts. They are...

Tide gauges are a unique source of information on past sea level changes over the 20 th century. However, these instruments can be affected by local ground motions, which are often poorly known. Here, InSAR can provide valuable information to understand the ground deformation context at city scale. In this study, we evaluate ground motion velocitie...

Indian Ocean is the home to many tropical low lying islands and highly populated coastal zones. Since a few recent decades, many of these zones have been gaining a lot of international attention due to fears of sea level rise and possible submersions of islands. In this study we estimate sea level rise and regional sea level variability in Indian O...

gauge records are the primary source of sea level information over multidecadal to century timescales. A critical issue in using this type of data to determine global climate-related contributions to sea level change concerns the vertical motion of the land upon which the gauges are grounded. Here we use observations from the Global Positioning Sys...

The GNSS reflectometry technique provides geometric information on the environment surrounding the GNSS antenna including the vertical distance to a reflecting surface. We use sea-surface reflections of GPS signals, recorded as oscillations in signal-to-noise ratio (SNR), to estimate the GNSS to tide gauge (TG) levelling tie, and thus the ellipsoid...

We present a new approach to estimate precise long-term vertical land motion (VLM) based on double-differences of long tide gauge (TG) and short altimetry data. We identify and difference rates of pairs of highly correlated sea level records providing relative VLM estimates that are less dependent on record length and benefit from reduced uncertain...

Measuring sea-level in a global reference frame with sub-centimeter accuracy is a relevant challenge in the context of current global warming and associated sea-level rise. Global Navigation Satellite Systems (GNSS) can provide sea-level measurements directly referenced in an absolute geocentric frame. We present here the results of a multiinstrume...

Depuis la fin du XIXe siècle, le changement climatique a entraîné une élévation niveau marin global de l'ordre de 20 cm. Localement, la valeur observée peut cependant s'écarter sensiblement de cette tendance globale, non seulement parce-que l'élévation du niveau marin n'est pas uniforme, mais aussi en raison des mouvements verticaux du sol qui peuv...

In coastal low-lying urban areas, vertical ground motions can significantly exacerbate the hazards related to sea-level rise. However, their spatial extent, their temporal evolution, and even sometimes their existence are often poorly known. This study aims to monitor variable urban ground motion (uplift and subsidence) from 1993 to 2010 in the met...

Hourly sea level observations from tide gauges located in Tenerife Island and spanning the period 1927-2012 have been quality controlled and analyzed. The original observations, obtained from the digitization of handwritten log books, correspond to three nearby tide gauges with known benchmarks and datum continuity. A single and consistent sea leve...

http://www.livingplanet2013.org/abstracts/833211.htm

http://www.livingplanet2013.org/abstracts/833211.htm

This paper assesses historic changes in mean sea level around the coastline of the North Sea, one of the most densely populated coasts in the world. Typically, such analyses have been conducted at a national level, and detailed geographically wider analyses have not been undertaken for about 20 years. We analyse long re- cords (up to 200 years) fro...

Delta margins are subject to relatively high rates of land subsidence and have the potential to significantly exacerbate future changes in sea levels predicted by global warming models used in impact studies. Through a combined analysis of GPS and persistent scatterer interferometry data, we determine that most of the coastline of Alexandria has be...

The climate component of sea level variation displays significant spatial variability, and it is now possible to reconstruct how sea level varied globally and regionally over the past half century. The fact that sea level rose faster than the global mean since 1950 in the central Pacific stimulated a study of decadal shoreline changes in this regio...

The ULR analysis centre is participating to the IGS Repro2 campaign which aims at reanalysing worldwide GNSS data since 1994. The ULR has the particular aim of processing the densest network of GNSS stations nearby tide gauges whose data have been collected through the SONEL (www.sonel.org) data centre of the Global sea-level observing system (GLOS...

GPS position time series contain time-correlated noise. The estimated parameters using correlated time series data, as station velocities, are then more uncertain than if the time series data were uncorrelated. If the level of the time-correlated noise is not taken into account, the estimated formal uncertainties will be smaller. By estimating the...

Measuring sea-level in a global reference frame with subcentimeter accuracy is a relevant challenge in the context of current global warming and associated sea-level rise. Global Navigation Satellite Systems (GNSS) can provide sea-level measurements directly referenced in an absolute geocentric frame. We present here the results of a multi-instrum...

Mediterranean long-term (interannual to interdecadal) sea level variability is examined, paying particular attention to the processes responsible for the observed changes. The nucleus of the chapter focuses on mean sea level changes and its different contributors: the steric component (changes in the density of the water column due to changes in te...

Considerable efforts are being made worldwide to upgrade tide gauge networks using new technologies. Because of the unique location of the Kerguelen Islands, the measurement of sea level there has received particular attention, with up to four systems equipped with modern sensors functioning simultaneously (two pressure tide gauges, a radar tide ga...

Une grande partie des côtes mondiales subissent aujourd'hui une érosion préoccupante qui devrait augmenter avec l'élévation du niveau marin induite par le changement climatique. Cependant, la mobilité du trait de côte induite par les processus d'érosion dépend non seulement des variations du niveau marin, mais aussi de nombreux autres facteurs qu'i...

Three-dimensional ground deformation measured with permanent GPS stations in West Africa was used for investigating the hydrological loading deformation associated with Monsoon precipitation. The GPS data were processed within a global network for the 2003-2008 period. Weekly station positions were retrieved with a repeatability (including unmodele...

Vertical land movements arise from a wide range of natural and anthropogenic processes. They affect most coastlines and can significantly increase (or decrease) the rates of sea level rise expected from the sole climatic contributions of ocean thermal expansion and land-based ice melting, magnifying (or reducing) the impacts of sea level rise on th...

Sea level changes show significant regional variability due to variations in ocean temperature. In some oceanic regions, sea level has risen quicker than the global average. However, we show from some examples in the Pacific Ocean that even in those case, shoreline changes are often still controlled by other factors such as waves, extreme events or...

In this study, we extend the advanced approach of combining tide gauge and satellite altimetry data with supplemental equations from adjacent tide gauge records of at least 30 years of common data to investigate the relative importance of the nonclimate contribution of vertical land movement to the observed rates of sea level change along the coast...

More than 10 years (1996-2008) of weekly GPS solutions of 299 globally distributed stations have been used to quantify the impact of the reference frame definition and especially the size of the network on the estimated station positions, velocities, and residual position time series. For that purpose, weekly regional solutions (covering the Europe...

Mean sea level observations from an historical tide gauge located in Cadiz (Southern Spain) spanning the period 1880–1924 were recovered from national archives. Daily sea level averages stored in handwritten log books were digitized, quality controlled, and referred to the same benchmark. A careful analysis of all the high precision leveling survey...

GPS data reanalysis are common nowadays when aiming at the highest consistency of the estimated products for the whole data period. The University of La Rochelle Consortium (ULR) has carried out several GPS data reanalysis campaigns with an increasing tracking network, an improving processing strategy and the best available models. The objective of...

The relative importance of the non-climate contribution of vertical land movement to the observed rates of sea level change at the coast is investigated based on the last GPS solution of the ULR consortium. This solution stems from 17 years of GPS data (1994-2010) reanalyzed using state-of-the-art models and corrections. It includes 407 GPS station...

Large land movements due to a wide range of anthropogenic and tectonic processes are observed in the Gulf of Mexico. The observed spatial and time variability of these processes makes it difficult the estimation of the land movement signal in tide gauge records. To supplement the limited GPS data available in this region, we explored a relatively n...

The explosion of Krakatau volcano in 1883 generated one of the highest tsunami ever recorded by tide-gauges. In the North Atlantic, the only known tide gauges that have recorded the Krakatau tsunami are situated along the coast of France and UK. These records have been collected and reproduced by Symons (1888), but the reproductions are not of very...

Le réchauffement climatique d'origine anthropique induit une élévation du niveau marin qui, loin d'être uniforme, présente une variabilité régionale importante. Il est aujourd'hui possible de reconstituer comment cette composante climatique du niveau marin a varié au cours du dernier demi-siècle. On constate ainsi dans certaines régions de l'océan...

Cet article fait une synthèse des résultats obtenus par notre équipe de recherche et présente quelques progrès récents dans le domaine de la mesure et de la modélisation des principaux facteurs d’évolution des littoraux, du niveau marin, des vagues et tempêtes, et des réponses morphologiques et stratigraphiques des côtes sédimentaires. Les mesures...

Sea level rise is a major consequence of climate change and is expected to threaten many low-lying and highly populated areas in the world. However, our understanding of the potential consequences of this phenomenon is limited by (1) the availability of validated sea level time series at regional scales, and more importantly, (2) a relatively poor...

1] This study focuses on the effects of time correlation in weekly GPS position time series on velocity estimates. Time series 2.5 to 13 years long from a homogeneously reprocessed solution of 275 globally distributed stations are analyzed in terms of noise content and velocity uncertainty assessment. Several noise models were tested, including pow...

RÉSUMÉ Les marégraphes enregistrent les variations de la hauteur du niveau de la mer par rapport à une référence locale attachée au socle sur lequel ils reposent à la côte. Lʼinformation conte-nue dans leurs enregistrements va donc bien au-delà du seul phénomène de la marée océanique. Ce constat explique lʼin-térêt porté à cette observation par de...

Tide gauges measure sea level relative to a local reference point attached to the land upon which the gauges are grounded at the coast. Therefore, the information contained in the tide gauge records goes beyond the only ocean tide phenomenon. This explains the wide range of interest expressed by various communities for that type of observations. To...

A data archeology exercise was carried out on sea level observations recorded during the transit of Venus across the Sun observed in 1874 from Saint Paul Island (38°41′S, 77°31 E) in the southern Indian Ocean. Historical (1874) and recent (1994–2009) sea level observations were assembled into a consistent time series. A thorough check of the data a...

In the framework of the African Monsoon Multidisciplinary Analysis (AMMA) project, six permanent GPS receivers have been established over West Africa. The stations of Djougou (Benin), Niamey (Niger) and Gao (Mali) are in operation since June 2005 and those of Tamale (Ghana), Ouagadougou (Burkina-Faso), and Timbuktu (Mali) since May 2006. In order t...

The sea level trends estimated from the satellite altimetry observations (AVISO) in the Gulf of Mexico during 1992-2009 reveal a pronounced variability around a mean value of about 1.8 mm/yr. The sea level variability is mostly due to the Loop Current and related rings and eddies that dominate the circulation in the Gulf. We have applied several st...

The geocentric land movements can be estimated by differencing the geocentric sea level data from satellite altimeters and the relative sea level data from tide gauges. This approach assumes the observed ocean signals to be identical at both the tide gauge and the corresponding altimetry point. The geocentric land movements can be estimated by diff...

Sea level extremes and their temporal variability have been explored based on the hourly measurements at Marseille tide gauge for the period 1885–2008. A careful quality check has first been applied to the observations to ensure consistency of the record by eliminating outliers and datum shifts. Yearly percentiles have been used to investigate long...

More than ten years (1996-2008) of weekly GPS solutions of 299 globally distributed stations have been used to quantify the impact of the reference frame definition and especially the size of the network on the estimated station positions, velocities, and residual position time series. For that purpose, weekly regional solutions (covering the Europ...

A systematic survey of the historical French archives was initiated in 2004 to search for ancient sea level observations. Long term sea-level records are invaluable to study trends in sea level components in the context of climate change due to global warming. A large amount of records have been discovered, notably on the Charente-Maritime French A...

It is well known that the spatial distribution of sea level measurements throughout the Southern Ocean is sparse and mostly consists of datasets with short records. The PSMSL (Permanent Service for Mean Sea Level) has only a few sea level time series below 45° South and most of them are shorter than twenty years. The lack of observations constrains...

Ten years (1997–2006) of weekly GNSS solutions of 205 globally distributed stations have been used to investigate the impact of the reference frame definition on the estimated station velocities. For that purpose, weekly regional solutions (covering the European region) and global solutions have been, respectively, stacked to obtain regional and gl...

Space geodesy applications have mainly been limited to horizontal deformations due to a number of restrictions on the vertical component accuracy. Monitoring vertical land motion is nonetheless of crucial interest in observations of long-term sea level change or postglacial rebound measurements. Here, we present a global vertical velocity field obt...

We examined the sensitivity of estimates of global sea-level rise obtained from GPS-corrected long term tide gauge records to uncertainties in the International Terrestrial Reference Frame (ITRF) realization. A useful transfer function was established, linking potential errors in the reference frame datum (origin and scale) to resulting errors in t...

We installed two orthogonal Blum-Esnoult silica tiltmeters in an underground military facility close to the shore in Cherbourg (France). They have recorded the oceanic loading effects from March 2004 to July 2005. The signal to noise ratio is such that, within a period range from a few minutes to a few days, the main non-linear oceanic tides up to...

A network of six GPS receivers has been established over West Africa, as part of the instrumental setup of the African Monsoon Multidisciplinary Analysis (AMMA) and the Gravimetry and HYdrology in AFrica (GHYRAF) projects. The receivers are located in Djougou (Benin), Niamey (Niger), Gao (Mali), Tamale (Ghana), Ouagadougou (Burkina-Faso), and Timbu...

The sea level variability in the Gulf of Mexico has been studied over the period 1950-2007 using the tide gauge records and the special satellite altimetry data. The method involves the estimation of spatial patterns derived from Empirical Orthogonal Functions (EOF) analysis of altimetric data spanning the period 1993-2007. The dominant EOF modes a...

The relationship between the gyre-scale circulation of the North Atlantic, represented by air pressure near to the centre of the sub-tropical gyre, and sea level measured at the eastern boundary of the ocean has been investigated using records commencing in the middle of the 18th century. These time series are twice as long as those employed in an...

Sea level is one of the most useful oceanographic parameters. Sea level data are vital to scientists for studies of fluctuations in major ocean currents and global climate change, to engineers for the design of coastal installations, to a large community engaged in what is now called 'operational oceanography' (e.g. the provision of flood warnings...

Geodetic measurements of the vertical crustal displacement collocated with absolute gravity changes provide a discriminatory measurement of present-day glacial changes, versus more deeply seated rock motions caused by glacial isostatic adjustment (GIA). At the East Antarctic station of Dumont d'Urville, we compare the displacements derived from con...

The results from a carefully implemented GPS analysis, using a strategy adapted to determine accurate vertical station velocities, are presented. The stochastic properties of our globally distributed GPS position time series were inferred, allowing the computation of reliable velocity uncertainties. Most uncertainties were several times smaller tha...